Electronic-Thermal Engineering of Semiconducting and Metallic Single-Walled Carbon Nanotube Field Emitters via Matrix-Driven Thermionic Field Emission

Single-walled carbon nanotubes (SWCNTs) are promising candidates for field emission (FE) sources. However, the relative superiority of semiconducting SWCNTs (S-SWCNTs) versus metallic SWCNTs (M-SWCNTs) under operating conditions remains controversial. Here, we demonstrate that FE performance can be strategically tailored via “electronic-thermal engineering” by exploiting the interplay between the density of states (DOS) in the nanotube and localized Joule heating. Evaluations using “sandwiched” and “blended” devices incorporating carbonized polymer matrices with controlled resistivities indicated that M-SWCNTs initiated electron emission at lower fields regardless of the device architecture because their electrons occupy the Fermi level. In low-resistivity blended configurations, where the matrix acts as an effective heat sink, M-SWCNTs retained their superiority via cold FE, achieving a turn-on field of 6.21 V/μm. Conversely, in high-resistivity sandwich architectures, a remarkable performance reversal occurred at higher applied fields: S-SWCNTs ultimately outperformed M-SWCNTs with lower turn-on and threshold fields of 6.38 and 7.44 V/μm, respectively (compared with 6.96 and 8.22 V/μm for M-SWCNTs, respectively). This inversion originates from high interfacial and junction resistances that induce intense localized Joule heating. M-SWCNTs efficiently dissipate heat via ballistic transport. By contrast, significant localized temperature increase in S-SWCNTs alters the Fermi−Dirac distribution, populating the high-DOS conduction band and triggering thermionic FE. Linear Fowler−Nordheim plots confirmed that quantum tunneling remains dominant, consistent with the Murphy−Good theory. These findings establish internal thermal management as a critical design principle for optimizing next-generation vacuum microelectronics.